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over EXPRESS is that the structure of a data model can be presented in a more understandable manner. A disadvantage of EXPRESS-G is that complex constraints cannot be formally specified. Figure 1 is an example. The data model presented in figure could be used to specify the requirements of a database for an audio compact disc (CD) collection.

Simple example

A simple EXPRESS data model looks like fig 2, and the code like this: SCHEMA Family; ENTITY Person ABSTRACT SUPERTYPE OF (ONEOF (Male, Female)); name: STRING;

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